Known in the art is the production of cements that includes, apart from Portland cement clinker and gypsum, the additional use of active mineral additives, the weight fraction of which accounts for 5 to 60% by mass. Introduction of active mineral additives into cement makes it possible to cut down its cost and in some cases to modify the construction and engineering properties of cement (for instance cement hardening kinetics, heat release, setting periods, resistance to sulphates).
Both artificial and natural mineral additives can be used as active mineral additives in cement production. Natural mineral additives include: diatomite, tripolite, opoka, melilite marble aggregate. Artificial mineral additives include blast furnace and phosphatic slags.
Natural mineral additives have low whiteness and hydraulic activity, which the whiteness of Portland cement and its construction and engineering properties.
Known in the art is an active mineral additive, which is a heat treated mixture (at 1350.degree.-1450.degree. C.) of phosphatic slag (92-99% by mass) and sodium sulphate (1-8% by mass) (SU, A, 893925). The whiteness coefficient of such mineral active additives, according to the absolute scale, is considerably higher than that of natural mineral additives and amounts to 89-93% and the hydraulic activity of this additive determined by the amount of lime absorbed by the additive in 15 titrations is 22.9-23.8 mg.
Known in the art is also an active mineral additive, that is subjected to melting at 1350.degree.-1450.degree. C. mixture of phosphatic slag, sodium sulphate and magnesium sulphate.
The use of such mineral additive fails to considerably enhance the whiteness, and hydraulic activity of cement.